The U.S. Food and Drug Administration has given the green light for the third dose of Covid vaccine to people with weak immune systems, to protect them from the Delta variant. The decision affects millions of Americans such as transplant recipients or cancer patients.

Anthony Fauci, director of the US Institute for Infectious Diseases and top expert of the Biden administration on the pandemic explained that the data on immunity granted by vaccines already administered are monitored by experts in real time “literally weekly”, observing the duration in population groups different for age, sex, health.